Cooling tower with indirect heat exchanger

ABSTRACT

A heat exchange apparatus is provided with an indirect evaporative heat exchange section and a direct evaporative heat exchange section. The indirect evaporative heat exchange section is usually located above the direct evaporative heat exchange section, and an evaporative liquid is passed downwardly onto the indirect heat exchange section. The evaporative liquid that exits the indirect evaporative heat exchange section then passes downwardly across and through the direct heat exchange section. The evaporative liquid is collected in a sump and then pumped upwardly to be distributed again across the indirect heat exchange section. The indirect heat exchange section is comprised of a plate type heat exchanger.

BACKGROUND OF THE INVENTION

The present invention relates generally to an improved heat exchangeapparatus such as a closed circuit fluid cooler, fluid heater,condenser, evaporator, thermal storage system, air cooler or air heater.More specifically, the present invention relates to a combination orcombinations of separate indirect and direct evaporative heat exchangesections

or components arranged to achieve improved capacity and performance.

The invention includes the use of a plate type heat exchanger as anindirect heat exchange section. When compared with coil circuit indirectheat exchangers which are comprised of individual circuits of tubing,the performance of an indirect heat exchange section comprised of aplate type heat exchanger is improved. Such indirect heat exchangesection can be combined with a direct heat exchange section, whichusually is comprised of a fill section over which an evaporative liquidsuch as water is transferred, usually in a downwardly streamingoperation. Such combined indirect heat exchange section and direct heatexchange section together provide improved performance as an overallheat exchange apparatus such as a closed circuit fluid cooler, fluidheater, condenser, evaporator, air cooler or air heater.

Part of the improved performance of the indirect heat exchange sectioncomprising a plate heat exchanger is the capability of the indirect heatexchange section as a plate type heat exchanger to provide both sensibleand latent heat exchange with the evaporative liquid which is streamedor otherwise transported over and through the indirect heat exchangesection. Another important improvement is that plate heat exchangerswill have more surface area in the same physical space as otherevaporative indirect heat exchangers. Such as indirect heat exchangerscomprised of serpentine coils.

Various combinations of the heat exchange arrangements are possible inaccordance with the present invention. Such arrangements could includean arrangement wherein the indirect heat exchange section operatesalone, is physically located above the direct heat exchange section oris physically located below the direct heat exchange section. In such anarrangement with indirect section located above the direct section, anevaporative liquid is streamed or otherwise sprayed downwardly onto theindirect heat exchange section with such evaporative liquid, which isusually water, then exiting the indirect section to be transported overthe direct heat exchange section which is usually comprised of a fillarrangement. In another arrangement of a combined heat exchangeapparatus the indirect heat exchange section is physically located belowthe direct heat exchange section. In another arrangement of a combinedheat exchange apparatus two or more indirect sections are placed in asingle closed circuit fluid cooler or heat exchanger each above or belowa direct heat exchange section is also part of the present invention.Further, it should be understood that due to varying heat loads andneeds of heat exchange, the heat exchanger apparatus or fluid cooler ofthe present invention could be operated wherein both air and anevaporative liquid such as water are drawn or supplied across both theindirect and direct heat exchange sections. It may be desirable tooperate the heat exchanger without a supply of the evaporative liquid,wherein air only would be drawn across the indirect heat exchangesection. It is also possible to operate a combined heat exchanger inaccordance with the present invention wherein only evaporative liquidwould be supplied across or downwardly through the indirect heatexchange section and the direct heat exchange section, and wherein airwould not be drawn by typical means such as a fan.

In the operation of an indirect heat exchange section, a fluid streampassing through the internal openings in the plate type heat exchangeris cooled, heated, condensed, or evaporated in either or both a sensibleheat exchange operation and a latent heat exchange operation by passingan evaporative liquid such as water together with air in passagesbetween individual plate pairs or cassettes in the indirect heatexchanger. Such combined heat exchange results in a more efficientoperation of the indirect heat exchange section. The evaporative liquid,which again is usually water, which passes across or downwardly throughthe indirect heat exchange section then passes, usually downwardly,across or through the direct heat exchange section which is typically afill assembly. Heat in the evaporative liquid is passed to air which isdrawn generally downwardly, upwardly or across the direct heat exchangesection and outwardly from the closed circuit fluid cooler or heatexchanger assembly by an air moving system such as a fan. Theevaporative liquid draining from the indirect or direct heat exchangesection is typically collected in a sump and then pumped upwardly forredistribution across the indirect or direct evaporative heat exchangesection. Of course, as explained above, the indirect and direct heatexchange sections can be reversed wherein, in the reversed situationwhere a direct heat exchange section would be located above an indirectheat exchange section, the evaporative fluid exiting the indirectsection would be collected in a sump and pumped upwardly fordistribution across the direct heat exchange section. Alternatively,only the indirect heat exchange section may be present.

Accordingly, it is an object of the present invention to provide animproved heat exchange apparatus, which could be a closed circuit fluidcooler, fluid heater, condenser, evaporator, air cooler or air heater,which includes an indirect heat exchange section and possibly a directheat exchange section.

It is another object of the present invention to provide an improvedheat exchange apparatus such as a closed circuit fluid cooler, fluidheater, condenser, evaporator, air cooler or air heater, including anindirect heat exchange section that comprises a plate type heatexchanger.

It is another object of the invention to provide an improved heatexchange apparatus comprising a plate type heat exchanger with moresurface area per volume than other evaporative indirect heat exchangers.

SUMMARY OF THE INVENTION

The present invention provides an improved heat exchange apparatus whichtypically is comprised of a combination of an indirect heat exchangesection and a direct heat exchange section. The indirect heat exchangesection provides improved performance by utilizing a plate type heatexchanger as the indirect heat exchange section. The plate type heatexchanger contains more surface area per unit volume that other indirectevaporative heat exchangers. The plate type heat exchanger is comprisedof one or more combined plate heat exchange groupings or cassettes eachcomprised of a pair of plates. Each cassette forms an internal passagebetween plates. Such plates are designed to allow a fluid stream to bepassed there through within the cassette, exposing the fluid stream to alarge surface area of one side of each plate in the cassette of the heatexchanger. Outside each plate a space is provided wherein air or anevaporative liquid such as water, or a combination of air and anevaporative liquid, can be passed to provide both sensible and latentheat exchange from the outside surfaces of the plates of the plate heatexchanger. Such utilization of a plate heat exchanger in the closedcircuit fluid cooler, fluid heater, condenser, evaporator, air cooler orair heater of the present invention provides improved performance andalso allows for combined operation or alternative operation wherein onlyair or only an evaporative liquid or a combination of the two can bepassed through or across the outside of the plates in the plate heatexchanger.

A direct heat exchange section is located generally beneath the indirectheat exchange section whereby the evaporative liquid filling from theindirect heat exchange section is allowed to pass across or through filland accordingly allow heat to be drawn from such evaporative liquid by apassage of air across or through the direct heat exchange section by airmoving apparatus such as a fan. Such evaporative liquid is collected ina sump in the bottom of closed circuit fluid cooler, fluid heater,condenser, evaporator, air cooler or air heater and pumped back fordistribution, usually downwardly, across or through the indirect heatexchange section.

It is also part of the present invention to provide an assembly whereintwo or more indirect heat exchange sections are located above two ormore direct heat exchange sections in a single cooling tower or heatexchanger unit. It is also part of the present invention to reverse thepositioning of the indirect and direct heat exchange sections whereinthe direct heat exchange section would be located above the indirectsection. Accordingly an evaporative liquid would be passed initiallydownwardly through the direct heat exchange fill section, with theevaporative liquid falling from the direct heat exchange section to theindirect heat exchange section.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 is a side view of a first embodiment of a heat exchanger inaccordance with the present invention;

FIG. 1A is a side view of another embodiment of a heat exchanger inaccordance with the present invention;

FIG. 2 is a side view of a second embodiment of a heat exchanger inaccordance with the present invention;

FIG. 3 is a side view of a third embodiment of a heat exchanger inaccordance with the present invention;

FIG. 4 is side view of a fourth embodiment of a heat exchanger inaccordance with the present invention;

FIG. 5 is a side view of a fifth embodiment of a heat exchanger inaccordance with the present invention;

FIG. 6 is a side view of a sixth embodiment of a heat exchanger inaccordance with the present invention;

FIG. 7 is a side view of a seventh embodiment of a heat exchanger inaccordance with the present invention;

FIG. 8 is a side view of an eighth embodiment of a heat exchanger inaccordance with the present invention;

FIG. 9 is a side view of a ninth embodiment of a heat exchanger inaccordance with the present invention;

FIG. 10 is a side view of a tenth embodiment of a heat exchanger inaccordance with the present invention;

FIG. 11 is a perspective view of a plate heat exchanger in accordancewith an embodiment of the present invention;

FIG. 12 is a partial view of a plate heat exchanger in accordance withan embodiment of the present invention;

FIG. 13 is a side view of a plate heat exchanger with plates separatedin accordance with the present invention;

FIG. 14 is a side view of a plate heat exchanger showing placesseparated in accordance with the present invention;

FIG. 15 is a top view of a plate heat exchanger in accordance with thepresent invention;

FIG. 16 is a perspective view of an assembled plate heat exchanger inaccordance with the present invention;

FIG. 17 is an end view of a plate heat exchanger in accordance with thepresent invention, and

FIG. 18 is a side view of a plate heat exchanger in accordance with thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1 of the drawings, a heat exchanger in accordancewith a first embodiment of the present invention is shown generally at10. Such heat exchangers generally are present in a closed circuitcooling tower with a direct heat exchange section 4 and an indirect heatexchange section 5 located above direct heat exchange section 4. Directheat exchange section 4 is typically comprised of fill usually comprisedof sheets of polyvinyl chloride. Direct heat exchange section 4 receivesair through air inlet 8 on the outside of heat exchanger 10, with airbeing drawn generally across and somewhat upwardly through direct heatexchange section 4 by fan 6. Indirect heat exchange section 5 is usuallycomprised of plate type heat exchanger 5A having a fluid outlet 2 and afluid inlet 1. It should be understood that the operation of fluidoutlet 2 and fluid inlet 1 can be reversed if it is desired. Thepreferred air direction through the indirect heat exchange section 5 isto enter from the top of the water distribution assembly 3. Air is thendrawn generally downwardly from the top through the indirect heatexchanger section 5 and exits from the bottom of section 5 by fan 6. Inaddition, air can also be optionally drawn through air inlet 7 andgenerally downwardly across and upwardly through indirect heat exchangesection 5 by fan 6 with the top of the water distribution assembly 7′open or closed. An evaporative liquid, usually water, flows downwardlyfrom water distribution assembly 3 such that the evaporative liquidfalls downwardly and through indirect heat exchange section 5. Theevaporative liquid that passes through indirect heat exchange section 5passes downwardly and through direct heat exchange section 4. Theevaporative liquid that passes downwardly and out from direct heatexchange section 4 is collected in sump 9A and is pumped upwardly bypump 9 for redistribution through water distribution assembly 3. Waterdistribution assembly 3 can be comprised of a variety of pipes withopenings, or any other water distribution arrangement such as usingspray nozzles, troughs, or other water distribution assemblies. Indirectheat exchange section 5 is usually comprised of a plate type heatexchanger 5A. A fluid to be cooled, condensed, heated, or evaporated,passes within the joined plates or cassettes of plate heat exchanger 5A.

Referring now to FIG. 1A of the drawings, a heat exchanger in accordancewith another embodiment of the present invention is shown generally at170. Such heat exchangers generally are present in a closed circuitcooling tower with a direct heat exchange section 174 and two indirectheat exchange sections 184 and 185 located above direct heat exchangesection 174. Direct heat exchange section 174 is typically comprised offill usually comprised of sheets of polyvinyl chloride. Direct heatexchange section 174 receives air through air inlet 178 on the outsideof heat exchanger 170, with air being drawn generally across andsomewhat upwardly through direct heat exchange section 174 by fan 175.The first indirect heat exchange section 184 is usually comprised ofplate type heat exchanger 184A having a fluid outlet 172 and a fluidinlet 171. The second indirect heat exchange section 185 is usuallycomprised of plate type heat exchanger 185A having a fluid outlet 182and a fluid inlet 181. It should be understood that the operation offluid outlets 172 and 182 and fluid inlets 171 and 181 can be reversedif it is desired. The preferred air direction through the indirect heatexchange sections 184 and 185 is to enter from the top of the waterdistribution assembly 173. Air is then drawn generally downwardly fromthe top through the indirect heat exchanger sections 184 and 185 andexits from the bottom of section 184 and 185 by fan 175. In addition,air can also be optionally drawn through air inlet 177 and generallydownwardly across and upwardly through indirect heat exchange section184 and 185 by fan 175 with the top of the water distribution assembly177A open or closed. An evaporative liquid, usually water, flowsdownwardly from water distribution assembly 173 such that theevaporative liquid falls downwardly and through indirect heat exchangesections 184 and 185. The evaporative liquid that passes throughindirect heat exchange sections 184 and 185 passes downwardly andthrough direct heat exchange section 174. The evaporative liquid thatpasses downwardly and out from direct heat exchange section 174 iscollected in sump 179A and is pumped upwardly by pump 179 forredistribution through water distribution assembly 173. Waterdistribution assembly 173 can be comprised of a variety of pipes withopenings, or any other water distribution arrangement such as usingspray nozzles, troughs, or other water distribution assemblies. Indirectheat exchange sections 184 and 185 are usually comprised of a plate typeheat exchanger 184 and 185A, respectively. Two fluids to be cooled,condensed, heated, or evaporated, pass independently within the joinedplates or cassettes of plate heat exchanger 184 and 185A as separatefluid streams.

FIG. 2 is a side view of the second embodiment of heat exchanger 20 inaccordance with a second embodiment of the present invention. Heatexchanger 20 is usually a closed circuit cooling tower including anindirect heat exchange section 15 located above a direct heat exchangesection 14, with the understanding that two such indirect and directsections are provided as part of heat exchanger 20. Direct heat exchangesection 14 is again comprised of fill sheets of a suitable material suchas polyvinyl chloride. Air to be passed across and generally crosswaysthrough direct heat exchange section 14 enters through air inlet 18 andis drawn by fan 16. Indirect heat exchange section 15 is usuallycomprised of a plate heat exchanger 15A. The preferred air directionthrough the indirect heat exchange section 15 is to enter from the topof the evaporative liquid distribution arrangement 13A. Air is thendrawn generally downwardly from the top through the indirect heatexchanger section 15 and exits from the bottom of section 15 by fan 16.In addition, air can also be optionally drawn downwardly, across andgenerally upwardly through indirect heat exchange section 15 enteringthrough air inlet 17 by fan 16 with the top of the liquid distributionarrangement 17′ open or closed. Evaporative liquid is provided to flowdownwardly from an evaporative liquid distribution arrangement 13A. Suchevaporative liquid passes generally downwardly across indirect heatexchange section 15. The evaporative liquid that exits indirect heatexchange section 15 passes downwardly through direct heat exchangesection 14 and is collected in sump 19A. Such collected evaporativeliquid is pumped by pump 19 upwardly for distribution to waterevaporative liquid distribution assembly 13A. Plate heat exchanger 15Aincludes fluid outlet 12 and fluid inlet 13, which can be reversed if itis desired. A fluid to be cooled, condensed, heated or evaporated passeswithin the joined plates or cassettes of plate heat exchanger 15A.

It should be understood in the operation of heat exchanger 10 and heatexchanger 20 described above, that depending on the performancerequired, both such heat exchangers may be operated with bothevaporative liquid exiting the evaporative liquid distribution systemand the fan drawing air across and through the direct and indirect heatexchange sections. If a lesser degree of heat exchange is required, itis possible to operate without the fan drawing air across the indirectand direct sections, such that only the evaporative liquid would exitand pass downwardly and through the indirect and direct heat exchangesections. Finally, the unit may be operated such that the evaporativeliquid would not be supplied through the evaporative liquid distributionassembly, and the heat exchanger would operate only with the fluidpassing within the indirect heat exchange section joined plate pairsbeing cooled by air passing downwardly or across and upwardly drawn bythe fan in the heat exchanger or cooling tower.

Referring now to FIG. 3 of the drawings, the third embodiment of a heatexchanger is shown generally at 30, in the form of a closed circuitcooling tower. Heat exchanger 30 is comprised of a direct heat exchangesection 34 which is located generally above an indirect heat exchangesection 35. Direct heat exchange section 34 is usually comprised of afill sheet assembly wherein the fill sheets are typically comprised ofpolyvinyl chloride. Air enters through air inlet 38 and is drawn by fan36 across and upwardly through direct heat exchange section 34. Anevaporative liquid usually water is distributed downwardly fromevaporative liquid distribution assembly 33; such evaporative liquidpasses downwardly and through direct heat exchange section 34. The top33A of the evaporative liquid distribution assembly 33, is usuallyclosed. Indirect heat exchange section 35 is usually comprised of aplate heat exchanger 35A which is comprised of a series of joined platecassettes with separated spaces between each cassette. Fluid to becooled, heated, condensed or evaporated enters through fluid inlet 31and exits through fluid outlet 32, although such can be reversed if itis desired. Air passes through the indirect heat exchange section 35 andbetween plate pairs or cassettes of the plate heat exchanger enteringthrough air inlet 37 and drawn by fan 36. Note that air inlet 38 can bepartially open to change the air flow ratio between the indirect and thedirect heat exchange sections or can be fully closed which allows thefull amount of air entering the direct heat exchange section.Evaporative liquid falling from direct heat exchange section 34 passesbetween the plate pairs or cassettes of plate heat exchanger 35 andprovides both sensible and latent heat transfer of the fluid passingwithin the joined plates in plate heat exchanger 35A. Such evaporativeliquid is collected in sump 39A and is pumped upwardly through usingpump 39 for redistribution through evaporative distribution assembly 33.

Referring now to FIG. 4, a fourth embodiment of a heat exchangerassembly is shown generally at 40 in accordance with the presentinvention. In this embodiment two direct heat exchanger sections 44 arelocated above two indirect heat exchanger sections 45. Evaporativeliquid exits evaporative liquid distribution assembly 43 and isdistributed downwardly through direct heat exchange section 44 which isusually comprised of a series of fill sheets made of polyvinyl chloride.The top 43A of the evaporative liquid distribution assembly 43, isusually closed. Air passed across and generally upwardly through directheat exchange section 44 entering through air inlet 48 and with airdrawn by fan 46. Note that air inlet 48 can be partially open to changethe air flow ratio between the indirect and the direct heat exchangesections or can be fully closed which allows the full amount of airentering the direct heat exchange section. Indirect heat exchangesection 45 is usually comprised of a series of plate heat exchangers45A. Such plate heat exchangers allow a fluid to be passed through thejoined plates or cassettes thereby exposing such fluid to a largesurface area of the plates themselves. Such plates are usually arrangedsuch that a space between each joined plate pair or cassette is providedfor the evaporative liquid to be passed there through, currently withair, to allow both sensible and latent heat transfer of the evaporativeliquid passing between the plates. Further air enters and passes acrossand upwardly through the plate heat exchanger 45. Air is drawn throughair inlet 47 and outwardly by fan 46. Evaporative liquid passingdownwardly through indirect heat exchange section 45 is collected insump 49A and is pumped upwardly by pump 49 to be distributed againthrough evaporative liquid distribution assembly 43.

It should be understood in the operation of heat exchanger 30 and heatexchanger 40 described above, that depending on the performancerequired, both such heat exchangers may be operated with bothevaporative liquid exiting the evaporative liquid distribution systemand the fan drawing air across and through the direct and heat exchangesections. It is possible to operate without the fan drawing air acrossthe indirect and direct sections, such that only the evaporative liquidwould exit and pass downwardly and through the indirect and direct heatexchange sections. Finally, it is possible that the evaporative liquidwould not be supplied through the evaporative liquid distributionassembly, and the heat exchanger would operate only with the fluidpassing through the indirect heat exchange section joined plate pairs orcassettes being cooled, heated, condensed, or evaporated by air passingacross and upwardly there through drawn by the fan in the heat exchangeror cooling tower.

Referring now to FIG. 5, a fifth embodiment of the present invention isshown as a heat exchanger in a closed, circuit cooling tower assembly50. Such heat exchanger is shown to be comprised of a direct heatexchange section 54 located generally above two indirect heat exchangesections 55. Direct heat exchange section 54 is usually comprised of aseries of fill sheets with each fill sheet being comprised of polyvinylchloride. Each indirect heat exchange section is comprised of a plateheat exchanger arrangement having a fluid outlet 52 and a fluid inlet51, which can be reversed if it is desired. Air is drawn inwardlythrough air inlets 57 by fan 56. Evaporative liquid passes fromevaporative distribution assembly 53 downwardly and through direct heatexchange section 54. Evaporative liquid passing through direct heatexchange section 54 passes downwardly through both indirect heatexchange sections 55. Evaporative liquid passing from indirect heatexchange sections 55 is collected in sump 59A, and is pumped upwardly bypump 59 for distribution through evaporative liquid distributionassembly 53. Indirect heat exchange section 55 is comprised of acollection of joined plate pairs or cassettes 55A. Each plate pair isseparated such that evaporative liquid passing downwardly throughindirect heat exchange section 55 can draw heat from the fluid withinplate pairs 55A sensibly by contact with the outside of the plates. Allof the heat is eventually released to the air from the evaporative fluidin both latent and sensible fashions in the evaporative passage.

It should be understood in the operation of heat exchanger 50 describedabove, that depending on the performance required, such heat exchangermay be operated with both evaporative liquid exiting the evaporativeliquid distribution system and the fan drawing air across and throughthe direct and indirect heat exchange sections. It is possible tooperate without the fan drawing air across the indirect and directsections, such that only the evaporative liquid would exit and passdownwardly and through the indirect and direct heat exchange sections.Finally, it is possible again that the evaporative liquid would not besupplied through the evaporative liquid distribution assembly, and theheat exchanger would operate only with the fluid passing through theindirect heat exchange section plates being cooled, heated, condensed,or evaporated by air passing across and upwardly there through drawn bythe fan in the heat exchanger or cooling tower.

Referring now to FIG. 6, a sixth embodiment of the present invention isshown generally as heat exchanger 60, which is usually a closed circuitcooling tower. Heat exchanger or cooling tower 60 is seen to becomprised of indirect heat exchange sections 65. Each indirect heatexchange section 65 is seen to be usually comprised of plate heatexchangers 65A, which are present as assemblies. Indirect heat exchangesection 65 has a fluid outlet 61 and a fluid inlet 62, which can bereversed if it is desired. An evaporative liquid, usually water, isdischarged from evaporative liquid distribution assembly 63 generallydownwardly such that evaporative liquid passes downwardly and throughindirect heat exchange section 65. Air is seen to be drawn inwardlythrough air inlets 67 generally upwardly through indirect heat exchangesection 65 by fan 66. Further, evaporative liquid that passes throughindirect heat exchange section 65 is collected in sump 69A and is pumpedupwardly by pump 69 for redistribution through evaporative liquiddistribution assembly 63. Evaporative liquid 63 that passes throughplate heat exchanger 65 absorbs heat by contacting the large platesurface of plate heat exchanger 65A to absorb heat from the fluid withinplate pairs 65A in a sensible fashion. All of the heat is eventuallyreleased to the air from the evaporative fluid in both latent andsensible fashions in the evaporative passage.

It should be understood in the operation of heat exchanger 60 describedabove, that depending on the performance required, such heat exchangermay be operated with both evaporative liquid exiting the evaporativeliquid distribution system and the fan drawing air up and through theindirect heat exchange sections. If a lesser degree of heat exchange isrequired, it is possible to operate without the fan drawing air up andthrough the indirect section, such that only the evaporative liquidwould exit and pass downwardly and through the indirect section.Further, if the evaporative liquid would not be supplied through theevaporative liquid distribution assembly, and the heat exchanger wouldoperate only with the fluid passing through the indirect heat exchangesection plates being cooled, heated, condensed, or evaporated by airpassing up and upwardly there through drawn by the fan in the heatexchanger or cooling tower. Further, the heat exchanger may be operatedwith the fan drawing air up and through one of the two indirectsections, with or without the evaporative liquid being supplied.

Referring now to FIG. 7, a seventh embodiment of the present inventionis shown generally as heat exchanger 70, which is generally in the formof a closed circuit cooling tower. Heat exchanger 70 is seen to becomprised of a direct heat exchange section 74 for above two indirectheat exchange sections 75. Direct heat exchange section 74 is usuallycomprised of a series of fill sheets each comprised of polyvinylchloride. Each indirect heat exchange section 75 is seen to be comprisedof a series of joined plates or cassettes 75A with fluid outlet 72 andfluid inlet 71. These fluid inlet and outlet can be reversed if it isdesired. Evaporative liquid is discharged from evaporative distributionassembly 73 downwardly onto and through direct heat exchange section 74.Evaporative liquid that passes through direct heat exchange section 74passes downwardly and through indirect heat exchange sections 75.Evaporative liquid that passes through and out of indirect heat exchangesections 75 is collected in sump 79A and pumped upwardly by pump 79 fordistribution through evaporative liquid distribution assembly 73. Airenters heat exchanger 70 through air inlet 77 and is drawn inwardly bycentrifugal fan 76 and pushed upwardly, or in a counter flow direction,with respect to the evaporative liquid, through indirect heat exchangesection 75 and direct heat exchange section 74. Evaporative liquid thatpasses through indirect heat exchange section 75 passes between thejoined plates or cassettes of plate heat exchangers 75A therebyproviding cooling, heating, evaporating, or condensing to the fluidpassing through the joined plate pairs of plate heat exchangers 75A.Further, the evaporative liquid passes downwardly through indirect heatexchange section 75 passes between the joined plates of plate heatexchanger 75A along with air to thereby allow both sensible and latentheat exchanges of the fluid passing through the joined plate pairs ofheat exchanger 75A.

It should be understood in the operation of heat exchanger 70 describedabove, that such heat exchanger may be operated with both evaporativeliquid exiting the evaporative liquid distribution system and the fandrawing air up and through the direct and indirect heat exchangesections. It is possible to operate without the fan drawing air up andthrough the indirect and direct sections, such that only the evaporativeliquid would exit and pass downwardly and through the indirect anddirect heat exchange sections. Finally, it is possible again that theevaporative liquid would not be supplied through the evaporative liquiddistribution assembly, and the heat exchanger would operate only withthe fluid passing through the indirect heat exchange section platesbeing cooled, heated, condensed, or evaporated by air passing upwardlythere through drawn by the fan in the heat exchanger or cooling tower.

Referring now to FIG. 8, an eighth embodiment of the heat exchanger inaccordance with the present invention is shown generally at 80 which isshown in the form of heat exchanger or closed circuit cooling tower.Heat exchanger 80 is seen to be comprised of a pair of indirect heatexchange sections 85. Each indirect heat exchange section 85 iscomprised of a series of joined plates or cassettes 85A. Indirect heatexchange section 85 also includes a fluid outlet 81 and fluid inlet 82,which can be reversed as it is desired. Evaporative liquid is providedby evaporative liquid distribution assembly 83 to pass downwardly andthrough each indirect heat exchange section 85. Such evaporative liquidthat passes through indirect heat exchange sections 85 is collected insump 89A and is pumped upwardly by pump 89 back to evaporative liquiddistribution assembly 83. Air that is drawn in air inlet 87 bycentrifugal fan 86 passes generally upwardly or in a counter flowdirection through indirect heat exchange sections 85. Evaporative liquidthat passes through heat exchange section 85 passes between the joinedplate pairs or cassettes of plate heat exchanger 85A such that the fluidpassing through the joined plates of exchanger 85A is cooled, heated,condensed, or evaporated both sensibly and in a latent manner by suchevaporative liquid passing downwardly over the outer surface area of thejoined plates of plate heat exchanger 85A along with air.

It should be understood in the operation of heat exchanger 80 describedabove, that such heat exchanger may be operated with both evaporativeliquid exiting the evaporative liquid distribution system and the fandrawing air up and through the indirect heat exchange section. It ispossible to operate without the fan pushing air up and through theindirect section, such that only the evaporative liquid would exit andpass downwardly and through the indirect heat exchange section. Finally,it is possible again that the evaporative liquid would not be suppliedthrough the evaporative liquid distribution assembly, and the heatexchanger would operate only with the fluid passing through the indirectheat exchange section plates being cooled, heated, condensed, orevaporated by air passing upwardly there through pushed by the fan inthe heat exchanger or closed circuit cooling tower.

Referring now to FIG. 9, a ninth embodiment of the present invention isshown generally at 90 as a heat exchanger or a closed circuit coolingtower. Heat exchanger 90 is seen to be comprised of an indirect sections95. Indirect heat exchange section 95 is seen to be comprised of aseries of joined plates or cassettes 95A with fluid outlet 92 and fluidinlet 91. It should be understood that fluid outlet and fluid inlet 92and 91 can be reversed if it is desired. As the embodiment shown in FIG.9 of heat exchanger 90 is generally of a low profile arrangement,centrifugal fan 96 is seen to be located outside the structure of heatexchanger 90 to thereby draw air inwardly through the fan structure tobe passed generally upwardly through and across indirect heat exchangesection 95. Evaporative liquid is distributed downwardly fromevaporative liquid distribution assembly 93 to pass downwardly throughindirect heat exchange section 95. Such evaporative liquid that passesout from indirect heat exchange assembly 95 is collected in sump 99A andis pumped upwardly by pump 99 for redistribution through evaporativeliquid distribution assembly 93. Evaporative liquid that passes throughheat exchange section 95 passes between the joined plate pairs orcassettes of plate heat exchanger 95A such that the fluid passingthrough inside of the joined plates of exchanger 95A is cooled, heated,condensed, or evaporated both sensibly and in a latent manner by suchevaporative liquid passing downwardly over the outer surface area of thejoined plates of plate heat exchanger 95A along with air.

It should be understood in the operation of heat exchanger 90 describedabove, that such heat exchanger may be operated with both evaporativeliquid exiting the evaporative liquid distribution system and the fanpushing air up and through the indirect heat exchange section. It ispossible to operate without the fan pushing air up and through theindirect section, such that only the evaporative liquid would exit andpass downwardly and through the indirect heat exchange section. Finally,it is possible again that the evaporative liquid would not be suppliedthrough the evaporative liquid distribution assembly, and the heatexchanger would operate only with the fluid passing through the indirectheat exchange section plates being cooled, heated, condensed, orevaporated by air passing upwardly there through pushed by the fan inthe heat exchanger or cooling tower.

Referring now to FIG. 10, a tenth embodiment of the present invention isshown generally as a heat exchanger 100 or in the form of a closedcircuit cooling tower. Heat exchanger 100 is seen to be comprised of anindirect heat exchange section 105 located generally below a direct heatexchange section 104. Direct heat exchange section 104 is usuallycomprised of a series of fill sheets each comprised of a polyvinylchloride. Indirect heat exchange section 105 is usually comprised of aseries of plate heat exchanger pairs or cassettes 105A, having a fluidoutlet 101 and a fluid inlet 102. If it desired, such fluid inlet andoutlet can be reversed. Air is seen to be drawn inwardly by fan 106which is located outside the physical structure or attached to theoutside of the physical structure of heat exchanger 100. This is usuallycentrifugal fan 106 which brings air inwardly near the side or bottom ofheat exchanger 100 and near one end thereof such air is forced upwardlythrough and across indirect heat exchange section 105 and generallyupwardly in a counter-flow direction, with respect to the evaporativeliquid, through direct heat exchange section 104. Evaporative liquid isdistributed downwardly from evaporative liquid distribution assembly103. Such evaporative liquid passes downwardly through direct heatexchange section 104. The evaporative liquid that exits direct heatexchange section 104 passes downwardly through indirect heat exchangesection 105 and is collected in a sump 109A. Such collected evaporativeliquid is pumped from sump 109A by pump 109 back to water distributionassembly 103. Plate heat exchanger pairs or cassettes 105A are typicallyspaced from each other such that the fluid passing inside the plates ofplate heat exchanger 105 is cooled, heated, condensed, and evaporatedboth sensibly and in a latent manner by the evaporative liquid passingon the outside of the plate pairs of plate heat exchanger 105 and alsoby the air being drawn by a counter-current manner across and generallyupwardly through indirect heat exchange section 105.

It should be understood in the operation of heat exchanger 100 describedabove, that such heat exchanger may be operated with both evaporativeliquid exiting the evaporative liquid distribution system and the fanforcing air up and through the direct and indirect heat exchangesections. It is possible to operate without the fan forcing air up andthrough the indirect and direct sections, such that only the evaporativeliquid would exit and pass downwardly and through the indirect anddirect heat exchange sections. Finally, it is possible again that theevaporative liquid would not be supplied through the evaporative liquiddistribution assembly, and the heat exchanger would operate only withthe fluid passing through the indirect heat exchange section platesbeing cooled, heated, condensed, or evaporated by air passing across andupwardly there through forced by the fan in the heat exchanger orcooling tower.

Referring now to FIGS. 11 and 12, a view of a plate heat exchanger inaccordance with the present invention is shown generally at 110. Eachplate heat exchanger is shown to be comprised of a series of joinedpairs or cassettes of plates 116 spaced from each other. A fluid outletheader is shown at 112 and a fluid inlet header is shown at 114. Asshown in FIG. 12, in a detailed breakaway view, fluid outlet header 112is seen to include openings 118 such that fluid to be cooled, heated,evaporated or condensed may exit from within each plate pair 116.Further passageways 120 are shown between plates 116 such thatevaporative liquid and air can pass on the outside of plates 116 toprovide both sensible and latent heat transfer to the fluid passingwithin joined plate or cassettes 116 of plate heat exchanger 110. Eachplate cassette 116 is seen to include an internal fluid passageway 122that allows fluid to be cooled, heated, condensed, or evaporated toenter through fluid inlet header 114, pass through the interior ofjoined plate pairs or cassettes 116 and exit through openings 118 ineach plate pair to enter outlet header 112. Such plate heat exchangerassembly 110 is seen to include usually a Chevron, embossing, crosshatch, dimpled, micro structurally extended, or any other surfaceenhancement pattern on both sides of each cassette assembly 116 toprovide increased surface area and turbulent flow to allow improvedperformance and heat exchange between the fluid within the each cassette116 and the air and evaporative liquid passing on the outside surface ofeach cassette 116. The geometries of the surface enhancement pattern onthe plate are strategically selected such that the passageway formed inthe space between each cassette assembly 116 allows good heat and masstransfer between the air and the evaporative liquid which passconcurrently between each cassette 116. This external passageway isusually, but not limited to, a general criss-cross pattern formed as thechevron patterns from adjacent cassettes approach close to, or evencontacting, each other. Such arrangement leads to the overall improvedperformance in all the embodiments of the heat exchanger of the presentinvention that include an indirect heat exchange section. The surfacepattern could be different on each side of the plate. The plate surfacecould be chemically treated (i.e., nano spray coated) to achieve anoptimized surface tension value and thus enhance the air and evaporativeliquid interaction.

Referring now to FIG. 13, a plate heat exchanger in accordance with thepresent invention is shown generally at 130. Each such plate heatexchanger is seen to be comprised of a series of adjacent plate pairs orcassettes 136. Each plate cassette 136 has an internal spacing within toallow a fluid to enter through fluid inlet header 134 pass within eachplate cassette 136 and exit through fluid outlet header 132. Each inletheader includes a spacer ring 134A to allow header 134 to be affixed tothe series of plate cassettes 136, and an outlet header spacer ring 132Ato allow fluid outlet header 132 to be attached to the series of platecassettes 136. Further, spacing 138 is seen in an exploded arrangementto exist between each plate cassette 136 to provide an adequatepassageway for evaporative liquid to pass in a cross-current,parallel-current, counter-current or some combination thereofarrangement with assembled plates 136. Such spacing also allows for airto pass between such plates such air usually being drawn in across-current, counter-current, parallel-current fashion or somecombination thereof arrangement by fans within the heat exchanger. Suchspacing between plate cassettes allows for increased performance of theindirect heat exchange section comprised of plate heat exchanger 130 byallowing both sensible and latent heat exchange to occur between thefluid within each plate pair or cassette 136 and the evaporative liquidand air passing in the passageway between such plate pair or cassettes136. The internal passage within each plate cassette is labeled 139.

Referring now to FIG. 14, a perspective view of a plate heat exchangerassembly 140 is shown. Plate heat exchanger assembly 140 is seen to becomprised of a series of plate cassettes 146 each of which includes aninternal passageway to allow fluid to pass therein. Each plate cassetteis seen to ideally be comprised of a chevron or other surfacearrangement to provide increased surface area of each plate pair. Plateheat exchanger assembly 140 is seen to also comprise a fluid outletheader 142 connected to the series of plate cassettes by outlet headerspacer ring 142A, and a fluid inlet header 144 connected to the seriesof plate cassettes 146 by inlet header spacer ring 144A. Passageway 148is seen to be created by the extended surface on the outside of eachneighboring plate cassette 146 such that an evaporative liquid can beallowed to pass between each plate cassette 146 to provide sensiblecooling for the liquid passing within each plate cassette 146. Further,passageway 148 provides space between plate cassettes 146 such that aircan be drawn in a counter-current, parallel-current, cross-currentfashion, or some combination thereof arrangement between plate cassettes146 to also provide both sensible and latent heat exchange with theevaporative liquid and hence provide indirect cooling, heating,condensing, or evaporating for the fluid within plates 146. The spacers,149, are optional which provide extra structure support to the plateheat exchanger assembly 140 to prevent the extended surface fromcrushing when the plate heat exchanger assembly 140 is tightened bybolts. Also, the spacers 149 may be used to increase the width of thepassageway 148 beyond its natural value which is two times of the heightof the extended surface.

Referring now to FIGS. 15-18, a detailed view of plate heat exchangerassembly 150 is shown. Each plate heat exchanger assembly is seen to becomprised of a series of plate pairs or cassettes 156 with a fluidoutlet header 152 and a fluid inlet header 154. Each fluid inlet header154 is connected by a fluid inlet header space ring 154A and fluidoutlet header 152 is seen to be connected by a fluid outlet header spacering 152A. The series of plate pairs or cassettes 156 are seen to bespaced from each other by the extended surface pattern on the outside ofeach plate cassette 156. On each plate, the enhanced surface pattern ison both sides. It is composed of extended surfaces (peaks, 158A) anddownwardly extruded surfaces (valleys, 158B). The peaks 158A on one sideof the plate is the valleys 158B on the other side (and vice versa). Thevalleys 158B touch each other to form the internal passageways 159within the plate pair or cassette 156. The peaks 158A on the outsidesurface of each plate pair 156 touch the peaks of the neighboring platepair 156 to form the external passageway 158 (e.g., typically acriss-cross pattern) such that air and evaporative liquid can passoutside and between plate cassettes 156 to provide both good sensibleand latent heat exchanges. Each plate cassette 156 is seen to usuallyhave a Chevron or any other surface enhancement pattern on both sides ofeach cassette assembly 156 to provide increased surface area andturbulent flow to allow improved performance and heat exchange betweenthe fluid within the each cassette 156 and the evaporative liquidpassing between each cassette 156. The geometries of the surfaceenhancement pattern on the plate are strategically selected such thatthe external passageways 158 formed in the space between each cassetteassembly 156 allows good heat and mass transfer between the air and theevaporative liquid which pass concurrently outside and between eachcassette 156. This external passageway is usually, but not limited to, ageneral criss-cross pattern.

In all the embodiments of the present invention, the plates can becomprised of various steels such as stainless steel or other corrosionresistant steels and alloys. It is also possible that such plates can becomprised of other materials that would lead to good heat exchangebetween the fluid within the plate and the evaporative liquid or airpassing outwardly therefrom. Such materials could be aluminum or copper;various alloys, or plastics that provide corrosion resistance and goodheat exchange.

What is claimed is:
 1. A method of exchanging heat comprising the stepsof: providing a direct evaporative heat exchange section and an indirectheat exchange section, the indirect heat exchange section conducting afluid stream within a plurality of pathways, the direct heat exchangesection comprising a top and a bottom, the indirect heat exchangesection comprising a top and a bottom, the indirect heat exchangesection being placed generally above the direct heat exchange section,distributing an evaporative liquid generally downward onto and throughthe indirect heat exchange section such that indirect heat exchangeoccurs between the fluid stream within the plurality of pathways and theevaporative liquid, and hence indirectly exchanging heat with the fluidstream within the plurality of pathways in the indirect section,distributing substantially all of the evaporative liquid leaving theindirect heat exchange section generally downward onto the direct heatexchange section, wherein the indirect heat exchange section iscomprised of a plate type heat exchanger, the plate type heat exchangercomprised of a series of adjacent plate cassettes forming an alternatingarrangement of first series of flow passages and a second series of flowpassages, an inlet header and an outlet header operatively connected tothe first series of flow passages such that the fluid stream can passinto the first series of flow passages and out from the first series offlow passages, the second series of flow passages arranged such that theevaporative liquid can pass through the second series of flow passages.2. The method of exchanging heat of claim 1, further comprising:collecting substantially all of the evaporative liquid that exits thedirect heat exchange section, and pumping the collected evaporativeliquid upwardly such that it can be distributed generally downward ontoand through the indirect heat exchange section.
 3. The method ofexchanging heat of claim 1 wherein in the plate type heat exchangercomprised of a series of adjacent plate cassettes forming an alternatingarrangement of a first series of closed loop flow passages and a secondseries of open loop flow passages, each plate cassette in the series ofadjacent plate cassettes includes an enhanced surface pattern toincrease plate surface area, to increase the sensible heat transfer fromthe fluid stream within the closed loop first series of flow passages tothe evaporative liquid.
 4. The method of exchanging heat of claim 1wherein in the plate type heat exchange comprised of a series ofadjacent plate cassettes forming an alternating arrangement of a firstseries of closed loop flow passages and a second series of open loopflow passages, a second inlet header and a second outlet header areoperatively connected to a third series of closed loop flow passages inthe plate heat exchanger such that a second fluid stream can pass intothe third series of flow passages and out from the third series of flowpassages.
 5. The method of exchanging heat of claim 1 wherein two directheat exchange sections and two indirect heat exchange sections areprovided, with one indirect heat exchange section located generallyabove one direct heat exchange section, with the second indirect heatexchange section located generally above the second direct heat exchangesection.
 6. The method of exchanging heat of claim 1 wherein two directheat exchange sections are provided, with the indirect heat exchangesection located generally above both direct heat exchange sections. 7.The method of exchanging heat of claim 1 further comprising moving airthrough the indirect section and through the direct section, the airmoving through the indirect heat exchange section exchanging both heatand mass with the evaporative liquid moving through the indirect heatexchange section and hence indirectly exchanging heat with the fluidstream within the plurality of pathways in the indirect section the anmoving through the direct heat exchange section exchanging heat and masswith the evaporative liquid moving through the direct heat exchangesection.
 8. A method of exchanging heat comprising the steps of:providing an indirect heat exchange section, the indirect heat exchangesection conducting a fluid stream within a plurality of pathways, theindirect heat exchange section comprising a top and a bottom,distributing an evaporative liquid generally downward onto and throughthe indirect heat exchange section such that indirect heat exchangeoccurs between the fluid stream within the plurality of pathways and theevaporative liquid, and within the plurality of pathways in the indirectsection, wherein the indirect heat exchange section is comprised of aplate heat exchanger, the plate heat exchanger comprised of a series ofadjacent plate cassettes forming an alternating arrangement of a firstseries of flow passages and a second series of flow passages, an inletheader and an outlet header operatively connected to the first series offlow passages such that the fluid stream can pass into the first seriesof flow passages and out from the first series of flow passages, thesecond series of flow passages arranged such that the evaporative liquidcan pass through the second series of flow passages.
 9. The method ofexchanging heat of claim 8, further comprising: collecting substantiallyall of the evaporative liquid that exits the indirect heat exchangesection, and pumping the collected evaporative liquid upwardly such thatit can be distributed generally downwardly onto and through the indirectheat exchange section.
 10. The method of exchanging heat of claim 8wherein the plate heat exchanger comprised of a series of adjacent platecassettes forming an alternating arrangement of a first series of closedloop flow passages and a second series of open loop flow passages, eachplate cassette in the series of adjacent plate cassettes includes anenhanced surface pattern to increase plate surface area and to increasethe sensible heat transfer from the fluid stream within the closed loopfirst series of flow passages to the evaporative liquid moving throughthe second series of flow passages in the plate heat exchanger.
 11. Themethod of exchanging heat of claim 8 wherein in the plate heat exchangercomprised of a series of adjacent plate cassettes forming an alternatingarrangement of a first series of closed loop flow passages and a secondseries of open loop flow passages, a second inlet header and a secondoutlet header are operatively connected to a third series of closed loopflow passages in the plate heat exchanger such that a second fluidstream can pass into the third series of closed loop flow passages andout from the third series of flow passages.
 12. A method of exchangingheat comprising the steps of: providing a direct evaporative heatexchange section and an indirect heat exchange section, the indirectheat exchange section conducting a fluid stream within a plurality ofpathways, the direct heat exchange section comprising a top and abottom, the indirect heat exchange section comprising a top and abottom, the direct heat exchange section being placed generally abovethe indirect heat exchange section, distributing an evaporative liquidgenerally downward onto and through the direct heat exchange sectionsuch that direct heat exchange occurs, distributing substantially all ofthe evaporative liquid leaving the direct heat exchange sectiongenerally downward onto the indirect heat exchange section, wherein theindirect heat exchange section is comprised of a plate type heatexchanger, the plate type heat exchanger comprised of a series ofadjacent plate cassettes forming an alternating arrangement of firstseries of flow passages and a second series of flow passages, an inletheader and an outlet header operatively connected to the first series offlow passages such that the fluid stream can pass into the first seriesof flow passages and out from the first series of flow passages, thesecond series of flow passages arranged such that the evaporative liquidcan pass through the second series of flow passages.
 13. The method ofexchanging heat of claim 12, further comprising: collectingsubstantially all of the evaporative liquid that exits the indirect heatexchange section, and pumping the collected evaporative liquid upwardlysuch that it can be distributed generally downward onto and through thedirect heat exchange section.
 14. The method of exchanging heat of claim12 wherein in the plate type heat exchanger comprised of a series ofadjacent plate cassettes forming an alternating arrangement of a firstseries of closed loop flow passages and a second series of open loopflow passages, each plate cassette in the series of adjacent platecassettes includes an enhanced surface pattern to increase plate surfacearea, to increase the sensible heat transfer from the fluid streamwithin the closed loop first series of flow passages to the evaporativeliquid.
 15. The method of exchanging heat of claim 12 wherein in theplate type heat exchange comprised of a series of adjacent platecassettes forming an alternating arrangement of a first series of closedloop flow passages and a second series of open loop flow passages, asecond inlet header and a second outlet header are operatively connectedto a third series of closed loop flow passages in the plate heatexchanger such that a second fluid stream can pass into the third seriesof flow passages and out from the third series of flow passages.
 16. Themethod of exchanging heat of claim 12 wherein two direct heat exchangesections and two indirect heat exchange sections are provided, with onedirect heat exchange section located generally above one indirect heatexchange section, with the second direct heat exchange section locatedgenerally above the second indirect heat exchange section.
 17. Themethod of exchanging heat of claim 12 wherein two indirect heat exchangesections are provided, with the direct heat exchange section locatedgenerally above both indirect heat exchange sections.
 18. The method ofexchanging heat of claim 12 further comprising moving air through theindirect section and through the direct section, the air moving throughthe indirect heat exchange section exchanging both heat and mass withthe evaporative liquid moving through the indirect heat exchange sectionand hence indirectly exchanging heat with the fluid stream within theplurality of pathways in the indirect section the air moving through thedirect heat exchange section exchanging heat and mass with theevaporative liquid moving through the direct heat exchange section.